Please note: At any venue, it is possible to take both back-to-back workshops. If you take the second workshop as well, you will be introduced to new material.

On another note, following Heidi Jo’s helpful request, I’ve added a search field to my blog, at the top of the right-hand pane.

Carbon/Kiln Troubleshooting

I would like to answer a question here that I am frequently asked. It seems to be common that after firing overnight, you find your box still hot, with most of the carbon gone. The fired pieces are exposed, and sometimes suffer from overheating or oxidation.

This can be caused by the type of carbon you use, or by your kiln, or both.

Some carbons stay hot for a very long time after the firing is over, regardless of the type of box you use – even if you take the box out of the kiln after the cycle is over and place it in a cool place. If this is the case, I suggest switching to another type of carbon. I asked a carbon manufacturer what the difference could be between carbons for our specific application of sintering powder metal. He referred my question to a technician, who never got back to me. This application is new to carbon manufacturers, and hopefully we will have better answers in the future. What he did say, though, is that different manufacturers follow different activation processes, and that I should find the carbon that works for me and stick with it, since the manufacturer is most likely to follow the same activation processes consistently. So I’m passing his suggestion on to you. I am not recommending any specific type of carbon here, since you are most likely using different brands of clay.

In the same way, some kilns stay hot long after the cycle is over. I have three kilns, and I use the same box and carbon in all of them, but one of them stays hot too long while the others do not. It does not mean that something is wrong with the kiln and that you need to switch kilns. All it means is that you need to be aware of it and handle your firing accordingly.

For example, in this kiln I try to avoid firing overnight. I take the box out immediately after the second phase. It saves my pieces and I don’t loose carbon.

When I have no choice but to fire all three kilns overnight, I cover the box in that particular kiln loosely with a fiber blanket or a fiber board with a hole in it. It helps to a certain extent, especially if I fill the box with extra carbon to begin with. I do lose some carbon, but the pieces are usually fine.

And a reminder: I receive a lot of questions about the firing schedule. You will find answers to a lot of your questions if you refer to my 33-page instruction manual, linked in the right-hand pane of this blog. It includes discussions of the boxes, the carbon, how to fire, a compatibility chart (what clays can be fired with others), kiln programming instructions, firing schedule, the firing process, a checklist, and more.

This entry was posted on Saturday, January 15th, 2011 at 4:44 pm. You can follow any responses to this entry through the RSS 2.0 feed.
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